The Long-Lasting Enhancing Effect of Distigmine on Acetylcholine-Induced Contraction of Guinea Pig Detrusor Smooth Muscle Correlates with Its Anticholinesterase Activity

Abstract

Distigmine bromide (distigmine), a reversible, long-lasting cholinesterase (ChE) inhibitor, is used for the treatment of underactive bladder in Japan and has been shown to potentiate urinary bladder (UB) contractility. We studied the duration of distigmine's potentiating effects on acetylcholine (ACh)-induced UB contraction and its inhibitory effects on ChE activity, and compared that with those of other ChE inhibitors (neostigmine, pyridostigmine, and ambenonium). The duration of potentiating/inhibitory effects of ChE inhibitors, including distigmine, on ACh-induced guinea pig UB contraction/ChE activity was evaluated for 12 h following washout. Dissociation rate constants (k) of the inhibitors were also tentatively calculated based on the time courses of their ChE inhibitory effects. The potentiating effect of distigmine (10 −6 M) on AChinduced UB contraction and its inhibitory effect on ChE activity were significantly sustained 12 h after washout. The potentiating effect of other ChE inhibitors on ACh-induced UB contraction, however, was sustained only until 3 h after washout. The ChE inhibitory effects of these inhibitors dissipated in a time-dependent manner after washout, with more than 75% of ChE activity restored by 4 h after washout. The k values of ChE inhibitors approached 0.50 h −1 , except for distigmine, where k could not be determined. Compared with that of other ChE inhibitors, the potentiating effect of distigmine on UB contractile function was significantly more sustainable following washout, which was likely associated with its corresponding long-lasting ChE inhibitory effect. Distigmine may associate more strongly with UB ChE than other ChE inhibitors, which would partly explain its sustained effects.

Long-Lasting Inhibitory Effects of Distigmine on Recombinant Human Acetylcholinesterase Activity

“…Furthermore, the k diss values of pyridostigmine and neostigmine determined in the present study (0.51±0.05 and 0.66±0.03 h , respectively). 18) However, the value obtained for ambenonium with rhAChE (1.41±0.08 h ). Although we do not have a clear explanation for this difference at present, one plausible explanation could be the presence of Cl in the structure of ambenonium (Fig.…”

“…Therefore, our laboratory started pharmacological studies on the effects of distigmine on urinary bladder (UB) motility and has previously reported results supporting the clinical effectiveness and usefulness of distigmine. [10][11][12][13][14][15][16][17][18] The most remarkable pharmacological characteristic of distigmine was the persistence of its effect. In particular, distigmine was found to potentiate the UB internal pressure via the micturition reflex for more than 12 h. 17) Interestingly, the long-lasting potentiating effect of distigmine on intravesical pressure persisted even after distigmine disappeared from the blood.…”

“…17) In addition, the potentiating effect of distigmine on the acetylcholine (ACh)-induced contraction of isolated UB tissue lasted for 12 h after distigmine was removed. 18) Based on our pharmacological results, we have speculated about two possible mechanisms by which distigmine could exert its long-lasting effects on UB motility: 1) distigmine very strongly binds to acetylcholinesterase (AChE) and resists dissociation; 2) distigmine persists in UB plasma membranes and is gradually released to inhibit AChE. Of these two possibilities, we considered the former to be more likely and examined how long distigmine inhibited the AChE activity in isolated UB tissue.…”

“…Consequently, we have found that distigmine inhibited the AChE activity in isolated UB tissue for 12 h even after removal of the drug. 18) However, the previous study was performed using UB smooth muscle tissues. Therefore, the second possibility, i.e., that distigmine remains in UB smooth muscle plasma membranes and is slowly released, could not be excluded.…”

Distigmine Bromide Produces Sustained Potentiation of Guinea-Pig Urinary Bladder Motility by Inhibiting Cholinesterase Activity

“…Ito et al also reported that rat erythrocyte AChE inhibition by distigmine did not correlate with the plasma concentrations of this drug following oral administration. 22) The possibility that active metabolites of distigmine generated by hepatic metabolism contribute to these pharmacodynamic effects cannot be completely ruled out at present, although this seems unlikely because: 1) distigmine was reported to be excreted by the kidneys 24) using 14 C-labeled distigmine; 2) three chemical candidates that are predicted to be generated by decomposition of distigmine did not affect AChE activity 25) ; 3) distigmine-mediated enhancement of AChinduced contraction of guinea pig urinary bladder smooth muscle lasted for ≥12 h after washing out with distigmine-free solution 25) ; and 4) distigmine inhibited recombinant human AChE activities for >48 h after the separation of distigmine from the enzyme by centrifugation (our unpublished observation). One possible explanation for this discrepancy would thus be the retention of distigmine within urinary bladder tissues or a robust binding to AChE, which would sequester the compound at its site of action.…”